1. doc.: IEEE 802.15-<doc#>
<month year>
doc.: IEEE <doc#>
January 2016
doc.: IEEE a
Project: IEEE P Working Group for Wireless Personal Area Networks (WPANs)
Submission Title: Kookmin University PHY sub-proposal for ISC using a Compatible M-FSK Scheme (CM-FSK)
Date Submitted: January 2016
Source: Yeong Min Jang, Trang Nguyen, Hong Chang Hyun [Kookmin University]
Contact:
Re:
Abstract: This is a PHY sub-proposal using M-FSK based Modulation Scheme. Being compatible to rolling shutter image sensors, it is called Compatible M-FSK (CM-FSK).
Purpose: Call for Proposal Response
Notice: This document has been prepared to assist the IEEE P It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein.
Release: The contributor acknowledges and accepts that this contribution becomes the property of IEEE and may be made publicly available by P
Submission
Kookmin University
<author>, <company>

2. Content PHY design considerations System designs
January 2016
doc.: IEEE a
Content
PHY design considerations
Frame rate variation
Different sampling rates and shutter speeds
System designs
System architecture
Frequency band and frequency separation
Data packet structure
Asynchronous Decoding
PHY format and PHY modes
Appendix 1: Indoor hybrid Compatible M-FSK/N-PSK system
Appendix 2: Seaside communications using CM-FSK
Submission
Kookmin University

3. PHY design considerations for Compatible M-FSK (CM-FSK)
January 2016
doc.: IEEE a
PHY design considerations
for Compatible M-FSK (CM-FSK)
Submission
Kookmin University

4. Compatibility to varying-frame-rates
January 2016
doc.: IEEE a
Compatibility to varying-frame-rates
Symbol clock out …
symbol i
symbol (i+1)
Rolling camera sampling
Transform
frequency
symbol i
frequency
symbol i
frequency
symbol i/(i+1)
frequency
symbol (i+1)
frequency
symbol (i+1)
Majority voting
symbol i voting
symbol (i+1) voting
How to transmit the clock information along with the symbol?
Submission
Kookmin University

5. Different sampling rates/shutter speeds
January 2016
doc.: IEEE a
Different sampling rates/shutter speeds
In-band
Camera
shutter speed
Eye cut-off
Camera cut-off
~8 kHz
~200 Hz
In-band
lower
shutter speed
Eye cut-off
Camera cut-off
~200 Hz
Bandwidth =?
(shutter speed)
Frequency separation =?
(sampling rate)
The frequency band in use is upper limited by shutter speed of camera. Lower shutter speed narrows the available band for communications
Sampling rate (rolling sampling rate) is also a matter to utilize the usage of frequency band efficiently. E.g. the sampling rate defines the minimum value of frequency separation.
Submission
Kookmin University

6. CM-FSK for ISC January 2016 doc.: IEEE 802.15-16- 0014 -01-007a
Submission
Kookmin University

7. a data packet with the clock information
January 2016
doc.: IEEE a
System Architecture
Transmitter side
Receiver side
clock information (of a data packet): This scheme is similar to the C-OOK scheme in which asynchronous bits (Ab) represent the form of clock information. However, the data packet with clock information (called a symbol) is encoded using M-FSK technique.
Symbol clock
Clock information
Ab = 1
Ab= 0
Merger
Ab=1
data packet i
M-FSK Encoder
a frequency symbol i
a data packet with the clock information …
data packet i
Submission
Kookmin University

8. CM-FSK Modulation frequency band
January 2016
doc.: IEEE a
CM-FSK Modulation frequency band
In-band
Camera
shutter speed
Eye cut-off
Camera cut-off
~8 kHz
~200 Hz
Frequency band
Compatibility
[200Hz ; ~2 kHz]
Webcams,
Smartphone cameras (Auto-exposure is OFF)
[200Hz ; ~4 kHz]
The frequency band:
B = 2kHz to be compatible to low shutter speed cameras
B = 4kHz (or higher, up to < 8kHz) to be compatible to most of smartphone cameras.
Submission
Kookmin University

9. Spectrum peak and the corresponding frequency measurement
January 2016
doc.: IEEE a
CM-FSK frequency separation
Selected image resolution: 640x480
Spectrum peak and the corresponding frequency measurement
The peak value of the FFT spectrum is linear proportional to the modulation frequency of light
In our specific experiment
Center frequency values:
Frequency separation: ∆(FFT peak) ≥ 1 <=> ∆(frequency) ≥ Hz
𝑓= × 𝑟𝑜𝑙𝑙𝑖𝑛𝑔 𝑠𝑎𝑚𝑝𝑙𝑖𝑛𝑔 𝑟𝑎𝑡𝑒 𝑘𝐻𝑧
Submission
Kookmin University

10. Frequency separation January 2016 doc.: IEEE 802.15-16- 0014 -01-007a
∆(FFT peak) =3
Max (number of channel)= 4𝑘𝐻𝑧 𝐻𝑧 = 41 [channels]
FDM spectrum with frequency separation = Hz
∆(FFT peak) =1
Max (number of channel)= 4𝑘𝐻𝑧 𝐻𝑧 = 124 [channels]
FDM spectrum with frequency separation = Hz
Submission
Kookmin University

11. Data packet Structure and Encoding
January 2016
doc.: IEEE a
Data packet Structure and Encoding
Submission
Kookmin University

12. Data packet structure A symbol is N times repeated in transmission
January 2016
doc.: IEEE a
Data packet structure Ab
Data packet i
DS i (1)
DS i (2)
DS i (N)
frequency symbol (i-1)
frequency symbol i
frequency symbol (i+1)
DS: Data Sub-Packet; SF: Start Packet-Frame Symbol; Ab: Asynchronous bit(s)
Time Domain
Information of a symbol before encoding
A symbol is N times repeated in transmission
An asynchronous bit (represents the clock information of the data packet) is along with the packet in transmission.
Submission
Kookmin University

13. Encoding PHY modes (SHR and PHR)
January 2016
doc.: IEEE a
Encoding PHY modes (SHR and PHR)
fSF
f'SF
best compatible band
. . .
32 frequency
extended band
Camera
limit
~8 kHz
SHR and PHR design:
On the lowest-band among the CM-FSK PHY modes to ensure compatibility with low sampling-rate cameras.
Relationship between fSF and f’SF is for training
fSF is chosen as lowest frequency on the available bandwidth, e.g. 200Hz, to be easily detected.
f’SF = fSF + 33x ∆f to train different cameras which have different sampling rates.
Submission
Kookmin University

14. Encoding PHY modes Data frequency: fi = fSF + i.∆f (i=1; 2;…; 32)
January 2016
doc.: IEEE a
Encoding PHY modes
HCS
MCS ID
PSDU length
Reserved
SHR
symbols: 2
C32-FSK
Data frequency: fi = fSF + i.∆f (i=1; 2;…; 32)
Preamble frequency: f’SF = fSF + 33.∆f
PHY modes
Number of frequency
Data rate
Unit
I.2/ I.3 32 50
bps
I.4/ I..5 64 60
Reserved
128 70
Submission
Kookmin University

15. Encoding table (C32-FSK)
January 2016
doc.: IEEE a
Encoding table (C32-FSK)
C32-FSK encoding table
Symbol structure
Baud symbol
Frequency
fSF fo
00000 f1
00001 f2
. . .
11110
f31
11111
f32
f'SF
f33
bits: 1 4 Ab
Data packet
∆f = Hz (~ 100Hz)
B = [200Hz; 3400Hz]
Data frequency: fi = fSF + i.∆f (i=1; 2;…; 32)
Preamble frequency: f’SF = fSF + 33.∆f
Symbol rate: 5/10/15 (symbol/sec)
Submission
Kookmin University

16. Encoding table (C64-FSK)
January 2016
doc.: IEEE a
Encoding table (C64-FSK)
C64-FSK encoding table
Symbol structure
Baud symbol
Frequency
fSF fo
000000 f1
000001 f2
. . .
101110
f31
101111
f32
f'SF
f33
010000
f34
010001
f35
111110
f64
111111
f65
bits: 1 5 Ab
Data packet
∆f = 48.3 Hz (~ 50Hz)
B = [200Hz; 3500Hz]
Data frequency: fi = fSF + i.∆f (i=1; 2;…; 32; 34;35; …; 65)
Preamble frequency: f’SF = fSF + 33.∆f
Symbol rate: 5/10/15 (symbol/sec)
Submission
Kookmin University

17. Asynchronous Decoding
January 2016
doc.: IEEE a
Asynchronous Decoding
Submission
Kookmin University

18. Asynchronous Decoding example
January 2016
doc.: IEEE a
Asynchronous Decoding example
Ab=1
Ab=1
Symbol out
Ab=0
Image frame sequence
1-0100
Decoded symbol
along with Ab(s)
0-0011
0-0001
1-1110
0100
0011
1110
Ab =1
Ab=0
Ab=1
Group to vote
Majority voting result
CM-FSK solves the communications performance, and the asynchronous bits solve the frame rate variation.
Submission
Kookmin University

19. PHY frame format January 2016 doc.: IEEE 802.15-16- 0014 -01-007a
Submission
Kookmin University

20. Hence CM-FSK is more reliable in detection and synchronization
January 2016
doc.: IEEE a
Best Compatible Band
Camera
Physical
limit
Extended band
Camera
Physical
limit
CM-FSK scheme (on the compatible-band)
CM-FSK (extended band)
SHR symbol 1
HCS
MCS ID
PSDU length
Reserved
PSDU
SHR symbol 2
fSF
f’SF
SHR
PHR
SHR and PHR design:
This part should have compatibility to almost of rolling shutter cameras
CM-FSK is chosen because of its advantages of lower error rate compared to OOK:
Hence CM-FSK is more reliable in detection and synchronization
The frequency band for encoding SHR and PHR is the lowest band among proposed frequency bands to ensure the compatibility to any rolling shutter camera.
The PSDU (can keep CM-FSK scheme or switch to C-OOK scheme) is performed on extended band to achieve higher link rate in specific situations.
Submission
Kookmin University

21. CM-FSK PHY modes PHY header design:
January 2016
doc.: IEEE a
CM-FSK PHY modes
PHY header design:
All frequencies used for PHY header are on low- band of the available bandwidth (e.g. 200Hz – 3.5kHz). This is to be compatible to low sampling rate cameras.
SHR and PHR are allocated in a common band (low-band)
The length for each frequency symbol is constant throughout the frame between preamble, header, and payload
PSDU can be allocated to the extended band.
MCS indication
PHY modes
Data rate
Unit
I.2 (C32-FSK) 50
bps
I.3 (C32-FSK/2-PSK) 60
I.4 (C64-FSK/2-PSK) 70
I.5(C32-FSK/4-PSK) 80
Submission
Kookmin University

22. Indoor hybrid Compatible M-FSK/M-PSK system
January 2016
doc.: IEEE a
Appendix 1:
Indoor hybrid Compatible M-FSK/M-PSK system
Submission
Kookmin University

23. CM-FSK LEDs lighting January 2016 doc.: IEEE 802.15-16- 0014 -01-007a3
Camera FOV
Walking road
Top-floor LEDs
Walking direction 4 5
January 2016
doc.: IEEE a
CM-FSK LEDs lighting
In general way, multiple LEDs are grouped together in communications. This is to provide the brightness for indoor when LEDs seems to be dimmed at 50%.
Camera’s RoI
Camera sequentially exposes light row by row. To get the maximum length of a LED on the image, LEDs are hang up along the walking way.
Submission
Kookmin University

24. - Longer d is better for communications, but not power consumption.
January 2016
doc.: IEEE a
FOV d L H
Walking Speed = w (m/s)
LED 1
LED 2
LED 3
- Condition of LEDs separation in user moving environment: L ≤ 2H.tg(FOV/2)
- Longer d is better for communications, but not power consumption.
Example: H = 2m; FOV = 680 (Samsung S5); d = 1.2m (equal size of fluorescent lamp); L = 2.7m.
Walking speed is limited by connection switching algorithm between LEDs.
Submission
Kookmin University

25. Hybrid Compatible M-FSK/N-PSK: Benefits
January 2016
doc.: IEEE a
Hybrid Compatible M-FSK/N-PSK: Benefits
Advantages of M-FSK:
Support for multiple transmitters (LEDs). Frequency allocation is based on M-FSK to share the bandwidth to all LEDs. The M-FSK technique is to avoid interference efficiently.
Great support for rolling shutter receivers. The detection of frequency is much easier with rolling effect.
Additional advantage of N-PSK:
The N-PSK is additionally used to achieve higher data rate than just M-FSK. The higher link rate is helpful when a part of link rate must be shared for mitigating frame rate variation (by transmitting the asynchronous bits instead of data).
Additionally support for global shutter receivers (only 2-PSK, optional).
Submission
Kookmin University

26. Hybrid Compatible M-FSK/2-PSK
January 2016
doc.: IEEE a
Hybrid Compatible M-FSK/2-PSK
Reference_Phase LED
Data_Phase LED
Architecture #1 of LEDs-group transmitter employing the hybrid 2-PSK /CM-FSK modulation scheme.
LED 1 and LED 2 together transmit the clock information of data packets through phase (2-PSK technique). The phase difference between LEDs decide the asynchronous bit (bit 1 if two LEDs are same phase; and bit 0 if phases are inverse). This is to solve the frame rate variation.
The data packets are transmitted through M-FSK, allowing log2M bits data link rate per symbol.
Submission
Kookmin University

27. Hybrid Compatible M-FSK/2-PSK
January 2016
doc.: IEEE a
Hybrid Compatible M-FSK/2-PSK
2-PSK Modulation
Architecture #2 of LEDs-group transmitter employing the hybrid 2-PSK /M-FSK modulation scheme.
In N-PSK scheme, among three LEDs one is for transmitting a phase reference and the other two are for data phases. It means 2 bits are transmitted through 2-PSK.
The M-FSK still takes whole advantage of bandwidth without any interference to N-PSK transmission.
Submission
Kookmin University

28. Data rate of hybrid system
January 2016
doc.: IEEE a
Data rate of hybrid system
Modulation Scheme and Proposed System
Data rate 1
2-PSK and M-FSK combination:
(groups of 2-LED tubes)
Rbit = (K/2) x logM(#_frequency) x (symbol rate) 2
(groups of k-LED tubes)
Rbit = (K/k) x logM(#_frequency) x (symbol rate) 3
4-PSK and M-FSK combination:
(groups of 4-LED tubes)
Rbit = 6 x (K/4) x logM(#_frequency) x (symbol rate) 4
N-PSK and M-FSK combination:
Rbit = (k-1)log2N x (K/k) x logM(#_frequency) x (symbol rate)
where K: is the number of LED tubes
#_frequency: denotes the number of frequencies used for communications in M-FSK
Submission
Kookmin University

29. Seaside communications using CM-FSK
January 2016
doc.: IEEE a
Appendix 2:
Seaside communications using CM-FSK
Submission
Kookmin University

30. Prototype January 2016 doc.: IEEE 802.15-16- 0014 -01-007a
Prototype 1: Continuous symbols transmission along with the clock information (asynchronous bits)
Symbol structure
bits: 1
4/5 Ab
Data packet
symbol 3
symbol 1
symbol 2
The communications for this prototype is exactly same as mentioned.
Prototype 2: Burst mode (with inter-symbol guard time for low-rate PD communications)
Symbol structure x
Data packet
symbol 3
symbol 1
symbol 2
Inter-symbol
guard time
The purpose of inter-symbol guard time:
A guard time to mitigate frame rate variation, and
Also is a period for low-rate PD communications. PD communications is allocated in high band that is invisible to camera (>10 kHz).
Purpose of PD communications here:
Additional information broadcasting (more data)
Localization beacon. ISC provides direction of the lighthouse, while PD communication determines the distance from the lighthouse.
Submission
Kookmin University

31. Non-Imaging based ISC: An additional optical module
January 2016
doc.: IEEE a
Non-Imaging based ISC: An additional optical module
In order to collect light energy and distribute uniformly into 2D image sensor, an additional optical lens module is used in front of the camera lens.
Incoming beam
Rolling shutter camera
A type of Fresnel Lens
(to collect light energy)
Lighthouse LED
Image Sensor
Fresnel Lens
The beam output from Fresnel lens into camera will cover the entire of image sensor instead of focusing into an focal point.
Submission
Kookmin University